The present invention relates to a trough-type parabolic concentrator for a solar thermal power plant, which focuses incident solar radiation onto an absorber pipe in which a heat transfer medium flows that is heated by the concentrated solar radiation.
Parabolic concentrators of the trough type are implemented, for example, in so-called SEGS plants (Solar Energy Generating Systems) in California. The reflectors of these trough-type parabolic concentrators are made of self-supporting composite glass silvered on the rear face. Therefore, the support structure for the reflectors only has to bear the weight of the reflectors; a shaping support of the reflector is not required. Due to the great effort of producing and mounting these power plants, they operate economically only in the order of about 50 MW and more. The investment required for a power plant of this caliber is rather high, opposing the implementation of such power plants in various sunny, but economically weak regions of the world.
In the past, efforts have been made to simplify the structure of trough-type parabolic concentrators, so as to lower the costs for a power plant. As a reflector, thin anodized aluminum sheet was used, entailing a substantial reduction of weight compared to the silvered composite glass. There is a drawback, however, in that aluminum sheet does not have the self-supporting properties of composite glass. Thus supporting structures are required that support the aluminum sheet such that it is held in the parabolic shape. However, known supporting structures of aluminum or steel are rather complex and heavy, which is why they are correspondingly expensive.
From U.S. Pat. No. 4,249,514, a solar concentrator of lightweight structure comprising a plurality of adjacent segments is known. Each segment has two integral side members with stepped surfaces approximating a curvilinear shape. Reflector bars are fixed on the respective steps of the two side members. On the rear, the side members are supported by a truss structure. The truss structure is made of thin longitudinal struts and tensioning wires fastened thereto. In this solar concentrator, since the required shaping support for a reflector plate is not present, no continuous reflector plate can be installed that would have a better efficiency than single reflector bars. It is a disadvantage of the lightweight structure that the individual segments are not rigid in themselves so that each segment requires a support fastened to the ground, requiring extensive structural efforts.
It is an object of the present invention to provide a trough-type parabolic concentrator that has a simple stricture and may be implemented economically.